Method and apparatus for device-to-device communication

ABSTRACT

A method includes scheduling at least one resource for a Device-to-Device (D2D) transmission control channel (DCCH) carrying a D2D control information (D2DCI) message, transmitting, by a first UE, the DCCH on the at least one DCCH resource to at least one second UE, scheduling at least one resource for a D2D data channel (DDCH), and transmitting, by the first UE, the DDCH on the at least one DDCH resource to the at least one second UE. A UE includes one or multiple antenna, and a processing circuitry configured to schedule at least one resource for a DCCH, transmit the DCCH on the at least one DCCH resource, to at least one second UE through the one or more multiple antenna, schedule at least one resource for a DDCH, and transmit the DDCH on the at least one DDCH resource, to the at least one second UE.

CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 61/885,385 filed on Oct. 1, 2013entitled “DEVICE-TO-DEVICE BROADCAST COMMUNICATION CHANNEL DESIGN”. Theabove-identified provisional patent application is hereby incorporatedby reference in its entirety.

TECHNICAL FIELD

This disclosure relates generally to wireless communication systems.More specifically, this disclosure relates to a protocol fordevice-to-device (D2D) communications.

BACKGROUND

Traditionally, cellular communication networks have been designed toestablish wireless communication links between mobile devices and fixedcommunication infrastructure components (such as base stations or accesspoints) that serve users in a wide or local geographic range. However, awireless network can also be implemented utilizing only device-to-device(D2D) communication links without the need for fixed infrastructurecomponents. This type of network is typically referred to as an “ad-hoc”network. A hybrid communication network can support devices that connectboth to fixed infrastructure components and to other D2D-enableddevices.

D2D communication may be used to implement many kinds of services thatare complementary to the primary communication network or provide newservices based on the flexibility of the network topology. D2D multicastcommunication such as broadcasting or groupcasting is a potential meansfor D2D communication where mobile devices are able to transmit messagesto all in-range D2D-enabled mobile devices or a subset of mobile deviceswhich are members of particular group. Additionally networks may requiredevices to operate in near simultaneous fashion when switching betweencellular and D2D communication modes. As a result, there is a need forprotocols which can manage D2D communication in these hybrid deploymentscenarios.

SUMMARY

This disclosure provides a protocol for device-to-device (D2D)communications.

A method includes scheduling at least one resource for aDevice-to-Device (D2D) transmission control channel (DCCH) carrying aD2D control information (D2DCI) message, transmitting, by a first UE,the DCCH on the at least one DCCH resource to at least one second UE,scheduling at least one resource for a D2D data channel (DDCH), andtransmitting, by the first UE, the DDCH on the at least one DDCHresource to the at least one second UE.

In some embodiments, the DDCH comprises a D2D broadcast channel (DBCH).

In some embodiments, the method further includes configuring a set ofpotential resources for DCCH, listening on the set of the potential DCCHresources to detect a transmission, in a case where the transmission isnot detected, or a power of the transmission is below a given threshold,selecting a subset of the set of potential DCCH resources as the atleast one DCCH resource, in a case where the transmission is detected,or a power of the transmission is above the given threshold, configuringa backoff timer indicating a number of time units or slots wherein theUE will not attempt to contend for the DCCH.

In some embodiments, the subset of the set of potential DCCH resourcesis predefined or configured or indicated via higher layer signaling(DSIB).

In some embodiments, subsets of the set of potential DCCH resources areindexed in an order of frequency, and the subset selection starts fromone of: the lowest index, the highest index, a randomly selected index,and an index that is configured based on a higher layer configuration ora D2D identification (ID).

In some embodiments, at least one of the DCCH and the DDCH is configuredaccording to a time and frequency hopping pattern defined by time andfrequency hopping parameters.

In some embodiments, sets of the time and frequency parameterscorrespond to a range of D2D ID values.

In some embodiments, either of a higher layer and a L1 layer signals oneor multiple higher layer configuration parameters indicating whethereach of the DCCH and DDCH have a time and frequency hopping patternseparately.

In some embodiments, the multiple configuration parameters comprise afirst higher layer parameter indicating whether a time and frequencyhopping configuration applies to the DCCH, and a second higher layerconfiguration parameter indicating whether a time and frequency hoppingconfiguration applies to the DDCH.

In some embodiments, the multiple higher layer configuration parameterscomprise a frequency hopping pattern indicator and a time hoppingpattern indicator for DCCH, and a time hopping pattern indicator and afrequency hopping pattern indicator for DDCH.

A user equipment (UE) configured for D2D communications includes one ormultiple antenna, and a processing circuitry configured to schedule atleast one resource for a Device-to-Device (D2D) transmission controlchannel (DCCH) carrying a D2D control information (D2DCI) message,transmit the DCCH on the at least one DCCH resource, to at least onesecond UE through the one or more multiple antenna, schedule at leastone resource for a D2D data channel (DDCH), and transmit the DDCH on theat least one DDCH resource, to the at least one second UE.

A UE configured for D2D communications includes one or more multipleantenna, and a processing circuitry configured to receive at least oneresource for a DCCH carrying a D2DCI message through the one or moremultiple antenna from a first UE, receive at least one resource for aDDCH based on DCCH through the one or more multiple antenna from thefirst UE, and demodulate and decode at least one DDCH resource, usingthe D2DCI message.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller may beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that, in many if not most instances, such definitions applyto prior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure and its advantages,reference is now made to the following description, taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 illustrates an example wireless network according to thisdisclosure;

FIGS. 2A and 2B illustrate an example user equipment (UE) according tothis disclosure;

FIG. 3 illustrates an example eNodeB (eNB) according to this disclosure;

FIG. 4 illustrates an LTE device-to-device broadcast/groupcastcommunications protocol according to this disclosure;

FIG. 5 illustrates a network-assisted partial coverage D2Dcommunications protocol according to this disclosure;

FIG. 6 illustrates an out-of-network D2D communications protocolaccording to this disclosure;

FIG. 7 illustrates an example of configured UL resources for multipleD2D control and broadcast transmission channels according to thisdisclosure;

FIG. 8 depicts a flowchart for a contention-based control channel accessprotocol according to this disclosure;

FIG. 9 illustrates an example scenario of inter- and intra-groupresource coordination according to this disclosure; and

FIG. 10 illustrates an example time/frequency hopping pattern for twoUEs broadcast transmission resources according to this disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 10, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of this disclosure may beimplemented in any suitably arranged device or system.

The following documents and standards descriptions are herebyincorporated into the present disclosure as if fully set forth herein:3GPP Technical Specification No. 36.211, version 11.2.0 (“REF1”); 3GPPTechnical Specification No. 36.212, version 11.2.0 (“REF2”); 3GPPTechnical Specification No. 36.213, version 11.2.0 (“REF3”); 3GPPTechnical Specification No. 36.214, version 11.1.0 (“REF4”); 3GPPTechnical Specification No. 36.300, version 11.5.0 (“REF5”); 3GPPTechnical Specification No. 36.321, version 11.2.0 (“REF6”); 3GPPTechnical Specification No. 36.331, version 11.3.0 (“REF7”); and 3GPPDocument No. RP-122009, “Study on LTE Device to Device ProximityServices” (“REF8”).

FIG. 1 illustrates an example wireless network 100 according to thisdisclosure. The embodiment of the wireless network 100 shown in FIG. 1is for illustration only. Other embodiments of the wireless network 100could be used without departing from the scope of this disclosure.

As shown in FIG. 1, the wireless network 100 includes an eNodeB (eNB)101, an eNB 102, and an eNB 103. The eNB 101 communicates with the eNB102 and the eNB 103. The eNB 101 also communicates with at least oneInternet Protocol (IP) network 130, such as the Internet, a proprietaryIP network, or other data network.

Depending on the network type, other well-known terms may be usedinstead of “eNodeB” or “eNB,” such as “base station” or “access point.”For the sake of convenience, the terms “eNodeB” and “eNB” are used inthis patent document to refer to network infrastructure components thatprovide wireless access to remote terminals. Also, depending on thenetwork type, other well-known terms may be used instead of “userequipment” or “UE,” such as “mobile station,” “subscriber station,”“remote terminal,” “wireless terminal,” or “user device.” For the sakeof convenience, the terms “user equipment” and “UE” are used in thispatent document to refer to remote wireless equipment that wirelesslyaccesses an eNB, whether the UE is a mobile device (such as a mobiletelephone or smartphone) or is normally considered a stationary device(such as a desktop computer or vending machine).

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipment (UEs) within a coverage area of theeNB 102. The first plurality of UEs includes a UE 111, which can belocated in a small business (SB); a UE 112, which can be located in anenterprise (E); a UE 113, which can be located in a WiFi hotspot (HS);and a UE 114, which can be a mobile device (M) like a cell phone,wireless laptop, wireless PDA, or the like. The eNB 103 provideswireless broadband access to the network 130 for a second plurality ofUEs within a coverage area of the eNB 103. The second plurality of UEsincludes a UE 115 and a UE 116, which can be mobile devices (M). In someembodiments, one or more of the eNBs 101-103 can communicate with eachother and with the UEs 111-116 using 5G, LTE, LTE-A, WiMAX, or otheradvanced wireless communication techniques.

Various UEs 111-116 could also support device-to-device (D2D)communications in which the UEs communicate directly with one another.In this manner, the network 100 represents a hybrid communicationnetwork that allows a UE to connect both to a fixed infrastructurecomponent (such as an eNB 101-103) and to other D2D-enabled UEs.

Dotted lines show the approximate extents of the coverage areas of twocells 120 and 125, which are shown as approximately circular for thepurposes of illustration and explanation only. It should be clearlyunderstood that the cells 120 and 125 associated with the eNBs 102-103can have other shapes, including irregular shapes, depending upon theconfiguration of the eNBs and variations in the radio environmentassociated with natural and man-made obstructions.

As described in more detail below, components of the wireless network100 (such as the eNBs 101-103 and the UEs 111-116) support adevice-to-device communications protocol. Among other things, thedevice-to-device communications protocol allows UEs 111-116 to engage inD2D communications possibly in parallel with normal operations of theeNBs 101-103 and with devices connected to the eNBs 101-103.

Although FIG. 1 illustrates one example of a wireless network 100,various changes can be made to FIG. 1. For example, the wireless network100 could include any number of eNBs and any number of UEs in anysuitable arrangement. Also, the eNB 101 could communicate directly withany number of UEs and provide those UEs with wireless broadband accessto the network 130. Similarly, each eNB 102-103 could communicatedirectly with the network 130 and provide UEs with direct wirelessbroadband access to the network 130. Further, the eNB 101, 102, and/or103 could provide access to other or additional external networks, suchas external telephone networks or other types of data networks.

FIG. 2 illustrates an example UE 114 according to this disclosure. Theembodiment of the UE 114 illustrated in FIG. 2 is for illustration only,and the other UEs in FIG. 1 could have the same or similarconfiguration. However, UEs come in a wide variety of configurations,and FIG. 2 does not limit the scope of this disclosure to any particularimplementation of a UE.

As shown in FIG. 2, the UE 114 includes an antenna 205, a radiofrequency (RF) transceiver 210, transmit (TX) processing circuitry 215,a microphone 220, and receive (RX) processing circuitry 225. The UE 114also includes a speaker 230, a main processor 240, an input/output (I/O)interface (IF) 245, a keypad 250, a display 255, and a memory 260. Thememory 260 includes a basic operating system (OS) program 261 and one ormore applications 262.

The RF transceiver 210 receives, from the antenna 205, an incoming RFsignal transmitted by an eNB or another UE. The RF transceiver 210down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 225, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 225 transmits the processed basebandsignal to the speaker 230 (such as for voice data) or to the mainprocessor 240 for further processing (such as for web browsing data).

The TX processing circuitry 215 receives analog or digital voice datafrom the microphone 220 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the main processor240. The TX processing circuitry 215 encodes, multiplexes, and/ordigitizes the outgoing baseband data to generate a processed baseband orIF signal. The RF transceiver 210 receives the outgoing processedbaseband or IF signal from the TX processing circuitry 215 andup-converts the baseband or IF signal to an RF signal that istransmitted via the antenna 205.

The main processor 240 can include one or more processors or otherprocessing devices and execute the basic OS program 261 stored in thememory 260 in order to control the overall operation of the UE 114. Forexample, the main processor 240 could control the reception of forwardchannel signals and the transmission of reverse channel signals by theRF transceiver 210, the RX processing circuitry 225, and the TXprocessing circuitry 215 in accordance with well-known principles. Insome embodiments, the main processor 240 includes at least onemicroprocessor or microcontroller.

The main processor 240 is also capable of executing other processes andprograms resident in the memory 260. The main processor 240 can movedata into or out of the memory 260 as required by an executing process.In some embodiments, the main processor 240 is configured to execute theapplications 262 based on the OS program 261 or in response to signalsreceived from eNBs, other UEs, or an operator. The main processor 240 isalso coupled to the I/O interface 245, which provides the UE 114 withthe ability to connect to other devices such as laptop computers andhandheld computers. The I/O interface 245 is the communication pathbetween these accessories and the main processor 240.

The main processor 240 is also coupled to the keypad 250 and the displayunit 255. The operator of the UE 114 can use the keypad 250 to enterdata into the UE 114. The display 255 can be a liquid crystal display orother display capable of rendering text and/or at least limitedgraphics, such as from web sites. The display 255 could also represent atouchscreen.

The memory 260 is coupled to the main processor 240. Part of the memory260 could include a random access memory (RAM), and another part of thememory 260 could include a Flash memory or other read-only memory (ROM).

As noted above, the UE 114 could operate in a hybrid communicationnetwork in which the UE 114 communicates with eNBs 101-103 and withother UEs. As described in more detail below, the UE 114 supports adevice-to-device communications protocol that, with the assistance ofthe eNBs, allows the UE 114 to establish communication links with theneighboring UEs (even UEs in different cells).

Although FIG. 2 illustrates one example of UE 114, various changes canbe made to FIG. 2. For example, various components in FIG. 2 could becombined, further subdivided, or omitted and additional components couldbe added according to particular needs. As a particular example, themain processor 240 could be divided into multiple processors, such asone or more central processing units (CPUs) and one or more graphicsprocessing units (GPUs). Also, while FIG. 2 illustrates the UE 114configured as a mobile telephone or smartphone, UEs could be configuredto operate as other types of mobile or stationary devices. In addition,various components in FIG. 2 could be replicated, such as when differentRF components are used to communicate with the eNBs 101-103 and withother UEs.

FIG. 3 illustrates an example eNB 102 according to this disclosure. Theembodiment of the eNB 102 illustrated in FIG. 3 is for illustrationonly, and other eNBs of FIG. 1 could have the same or similarconfiguration. However, eNBs come in a wide variety of configurations,and FIG. 3 does not limit the scope of this disclosure to any particularimplementation of an eNB.

As shown in FIG. 3, the eNB 102 includes multiple antennas 305 a-305 n,multiple RF transceivers 310 a-310 n, transmit (TX) processing circuitry315, and receive (RX) processing circuitry 320. The eNB 102 alsoincludes a controller/processor 325, a memory 330, and a backhaul ornetwork interface 335.

The RF transceivers 310 a-310 n receive, from the antennas 305 a-305 n,incoming RF signals, such as signals transmitted by UEs or other eNBs.The RF transceivers 310 a-310 n down-convert the incoming RF signals togenerate IF or baseband signals. The IF or baseband signals are sent tothe RX processing circuitry 320, which generates processed basebandsignals by filtering, decoding, and/or digitizing the baseband or IFsignals. The RX processing circuitry 320 transmits the processedbaseband signals to the controller/processor 325 for further processing.

The TX processing circuitry 315 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 325. The TX processing circuitry 315 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 310 a-310 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 315 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 305 a-305 n.

The controller/processor 325 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 325 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 310 a-310 n, the RX processing circuitry 320, andthe TX processing circuitry 315 in accordance with well-knownprinciples. The controller/processor 325 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. For instance, the controller/processor 325 could support beamforming or directional routing operations in which outgoing signals frommultiple antennas 305 a-305 n are weighted differently to effectivelysteer the outgoing signals in a desired direction. Any of a wide varietyof other functions could be supported in the eNB 102 by thecontroller/processor 325. In some embodiments, the controller/processor325 includes at least one microprocessor or microcontroller.

The controller/processor 325 is also capable of executing programs andother processes resident in the memory 330, such as a basic OS. Thecontroller/processor 325 can move data into or out of the memory 330 asrequired by an executing process.

The controller/processor 325 is also coupled to the backhaul or networkinterface 335. The backhaul or network interface 335 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 335 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G, LTE, or LTE-A), the interface 335 could allow the eNB102 to communicate with other eNBs over a wired or wireless backhaulconnection. When the eNB 102 is implemented as an access point, theinterface 335 could allow the eNB 102 to communicate over a wired orwireless local area network or over a wired or wireless connection to alarger network (such as the Internet). The interface 335 includes anysuitable structure supporting communications over a wired or wirelessconnection, such as an Ethernet or RF transceiver.

The memory 330 is coupled to the controller/processor 325. Part of thememory 330 could include a RAM, and another part of the memory 330 couldinclude a Flash memory or other ROM.

As noted above, the eNB 102 could operate in a hybrid communicationnetwork in which UEs communicate with the eNBs 101-103 and with otherUEs. As described in more detail below, the eNB 102 supports anetwork-assisted multi-cell device discovery protocol that, with theassistance of the eNBs 101-103, allows the UEs to discover neighboringUEs and to establish communication links with the neighboring UEs (evenUEs in different cells).

Although FIG. 3 illustrates one example of an eNB 102, various changescan be made to FIG. 3. For example, the eNB 102 could include any numberof each component shown in FIG. 3. As a particular example, an accesspoint could include a number of interfaces 335, and thecontroller/processor 325 could support routing functions to route databetween different network addresses. As another particular example,while shown as including a single instance of TX processing circuitry315 and a single instance of RX processing circuitry 320, the eNB 102could include multiple instances of each (such as one per RFtransceiver). Also, various components in FIG. 3 could be combined,further subdivided, or omitted and additional components could be addedaccording to particular needs.

FIG. 4 illustrates an LTE device-to-device broadcast/groupcastcommunications protocol 400 according to this disclosure. The embodimentof the LTE device-to-device broadcast/groupcast communications protocol400 shown in FIG. 4 is for illustration only. Other embodiments could beused without departing from the scope of the present disclosure.

The D2D communication can be used to implement many kinds of servicesthat are complementary to the primary communication network or providenew services based on the flexibility of the network topology. The LTED2D multicast communication such as broadcasting or groupcasting hasbeen identified as a potential means for D2D communication where UEs areable to transmit messages to all in-range D2D-enabled UEs or a subset ofUEs which are members of particular group.

As illustrated in FIG. 4, two D2D communication groups 412 and 422 arewithin the communication range of eNB 402, and the D2D communicationgroup 432 is outside of the communication rage of the eNB 402. The UEsof the groups 412 and 422 perform a network-assisted partial coverageD2D communications, and UEs of the group 432 perform out-of-network D2Dcommunications. For example, future public safety networks are expectedto require devices to operate in near simultaneous fashion whenswitching between cellular and D2D communication modes. As a result,there is a need for protocols which can manage D2D communication inthese hybrid deployment scenarios.

FIG. 5 illustrates a network-assisted partial coverage D2Dcommunications protocol 500 according to this disclosure. In the exampleshown in FIG. 5, the network includes an eNB 502 and two D2D enabled UEs504, 506: UE1 502 which is within the communication range of the eNB 502and UE2 506 which is outside the coverage of the cellular network.Although only two UEs are considered, the following description could begeneralized to consider discovery between a plurality of UEs.

The eNB 502 can configure an in-network UE to perform as a relay using aD2D transmission channel due to knowledge of out-of-network D2D-enabledUEs (for example in the case of a D2D discovery protocol) or due to theimplementation of an emergency broadcast service which utilizesconfigured in-network UEs as coverage-extending relays.

Group leader determination could be based upon preconfiguration, forexample one device in a police precinct. Alternatively, group leaderdetermination could be based upon determination that no other groupleaders are active within the vicinity of a UE or group of UEs.

For example, a UE, such as UE 114, during the course of synchronizationprocedure, as previously described, can determine that neithernetwork-based nor D2D UE-based sync signal is received. Afterdetermining that neither network-based nor D2D UE-based sync signal isreceived, the UE 114 can determine to initiate group-leader operationand transmit D2D sync and/or D2D SIB.

The embodiments disclosed herein can also apply for the operationwherein all or a fraction of the devices to engage in D2D communicationare not within coverage of the cellular network. In this scenario,coordinated operation of the D2D protocol is desired in order toefficiently allocate resources and avoid potential interference issues.One method to implement this is through the operation of one of theout-of-coverage (OOC) UEs taking on much of the coordination andsignaling provided the eNB in the case of full or partial networkoperation. All or multiple UEs can be capable of operation as a groupleader, and the detailed procedure for group leader authorization andinitiation is described in U.S. patent application Ser. No. 14/266,024,the disclosure of which is incorporated by reference in its entirety.Although only two UEs are illustrated, the following description couldbe generalized to consider discovery between a plurality of UEs.

FIG. 6 illustrates an out-of-network D2D communications protocol 600according to this disclosure. The embodiment of the out-of-network D2Dcommunications protocol 600 shown in FIG. 6 is for illustration only.Other embodiments could be used without departing from the scope of thepresent disclosure.

FIG. 6 considers the operation wherein all of the devices to engage inD2D communication are not within coverage of the cellular network. Inthis scenario, coordinated operation of the D2D protocol is desired inorder to efficiently allocate resources and avoid potential interferenceissues. One method to implement coordinated operation of the D2Dprotocol is through the operation of one of the OOC UEs 602-604 takingon much of the coordination and signaling provided by the eNB in thecase of full or partial network operation. All or multiple UEs 602-604can be capable of operation as a group leader.

The protocol for the in-network coverage or out-of-network coverage D2Dtransmission protocol is divided into three main phases: 1.Synchronization/Configuration, 2. D2D Control Transmission/Reception,and 3. D2D data channel transmission and reception. The detaildescriptions on each phase are as follows.

D2D Synchronization

Timing synchronization must first be ensured so that the control anddiscovery signaling can be properly transmitted and received byin-coverage (IC) and out-of-coverage (OOC) devices. Several alternativesfor achieving timing synchronization between UE1 and UE2 are considered:UE1 transmits a periodic synchronous signal (denoted as D2D sync signal)to UE2 based upon the primary synchronization signals and secondarysynchronization signals (PSS/SSS) transmitted by the eNB; or UE1transmits a compact periodic synchronous signal, which has a shortduration and long periodicity and can cover the entire uplink ordownlink bandwidth.

Control Channel Resource Allocation

A D2D communication channel corresponds to a given group or broadcastID. In order for a D2D data channel (DDCH) transmission including a D2Dbroadcast channel (DBCH) to be received, a D2D transmission controlchannel (DCCH) is needed to be transmitted in addition to the referencesymbols (RS) and data symbols. This control information can be separatedfrom unicast cellular control information since the control informationis only relevant for UEs participating in D2D communication.

In certain embodiments, the D2D control information for a given group orbroadcast ID employs a unique DCCH. The group/broadcast IDs can bepre-configured, indicated by higher-layer configuration, or provided ina system information broadcast message. UEs can be capable to beconfigured to monitor or receive from multiple DCCHs. In anotheralternative, the control information for multiple groups or broadcastIDs can be mapped to the same DCCH.

A limited amount of DCCH information can be provided via systeminformation broadcast. This primarily concerns the information needed toacquire the DCCH(s). For example, this information can be carried bymeans of a single D2D specific SystemInformationBlock:SystemInformationBlockTypeX (DSIB). For example, the time/frequencyresources utilized for a given D2D channel can be divided into N D2Dtransmission resource blocks (DTRBs) transmitted in T dedicated D2Dtransmission resource slots (DTRS).

FIG. 7 illustrates an example of configured UL resources 700 formultiple D2D control and broadcast transmission channels according tothe present disclosure. The embodiment of configured UL resources formultiple D2D control and broadcast transmission channels in FIG. 7 isfor illustration only. Other embodiments could be used without departingfrom the scope of the present disclosure.

In one example, a DTRB corresponds to a PRB pair and a DTRS correspondsto a subframe. As illustrated in the FIG. 7, a set of DTRBs (PRB-pairs)is reserved within an uplink D2D DTRS (subframe) for D2D transmission.

A UE that wishes to transmit a D2D control information (D2DCI) messageon the DCCH must have allocated physical resources. Several embodimentsfor allocation of resources are considered.

In option 1-1, the resources allocated for the DCCH for a given UE arestatically preconfigured by the network or another entity.

In option 1-2, the resources allocated for the DCCH are semi-staticallyor dynamically from a set of available DCCH resources:

In option 1-2A, the network or a cluster-head controller UE indicatesthe subset of available resources to be used by the UE for DCCHtransmission. The indication can be semi-static via higher-layersignaling (e.g. DSIB) or dynamic (e.g. per DCCH transmissionopportunity) via physical layer signaling.

In option 1-2B, the network or a cluster-head controller UE indicates aset of available resources from which the UE can select a subset to beused by the UE for DCCH transmission. The indication can be semi-staticvia higher-layer signaling (e.g. DSIB) or dynamic (e.g. per DCCHtransmission opportunity) via physical layer signaling.

In option 1-2C, the UE can select a subset to be used for DCCHtransmission without prior explicit indication of available resources.

Control Channel Design and Access

Depending on the method of resource allocation as discussed in theControl Channel Resource Allocation above, the UE needs to access theDCCH on the selected resources. In the case of pre-configuration ornetwork or cluster head indication, the transmitting UE directlytransmits during the time slots and at the frequency locationsindicated. However, in the case of the options B and C, wherein the UEautonomously selects the resources collision between other UEs makingsimilar resource allocation selections should be addressed to avoidresulting DCCH interference.

FIG. 8 depicts a flowchart 800 for a contention-based control channelaccess protocol according to the present disclosure. While the signalingflow depicts a series of sequential signals, unless explicitly stated,no inference should be drawn from that sequence regarding specific orderof performance, performance of signals or portions thereof seriallyrather than concurrently or in an overlapping manner, or performance ofthe signals depicted exclusively without the occurrence of interveningor intermediate signals. The process depicted in the example depicted isimplemented by a transmitter chains in, for example, a mobile stationand a base station.

In one embodiment, a contention-based control channel access operationis utilized by a UE before transmitting on the DCCH. Thecontention-based control channel access operation begins with the step802, where a UE prepares to transmit on DCCH and configures theappropriate message and initializes the control channel accessprocedure. The amount of available resources for D2D broadcast operationmay not be sufficient in scenarios where a large number of UEs arelocated in a dense location (public safety UEs responding to anemergency incident). As a result, due to time/frequency resource reuse,a large amount of interference or contention delay can be incurred,resulting in poor throughput performance. Especially in the scenario ofgroupcast operation, it is desirable to distinguish resource allocationwithin a group and resource allocation between UEs in different groups.FIG. 9 illustrates an example scenario of inter- and intra-groupresource coordination.

In one embodiment, the initial set of possible DCCH resources aredetermined by the UE based upon the D2D-ID. For example, UEs can beorganized into groups based on ID or a single ID representing a group ofUEs can correspond to the D2D-ID. Based on this ID allocation, sets ofavailable DCCH resources can be partitioned as in FIG. 7 for example. Inone alternative this mapping can be preconfigured at the UE or indicatedvia higher layer signaling (e.g. DSIB).

Alternatively, if groupcast functionality is not present or only one setof DCCH resources are available for all UEs regardless of groupassociation, the D2D-ID to resource set mapping may not be required. Inthis case the UE can directly consider the set(s) of resources withoutsuch an ID mapping. However, the ID mapping can be implemented in a waythat is transparent from the UE perspective, wherein the UE is not awareof what other potential sets of resources may or may not be availableother than those corresponding to its respective ID.

Once the UE has a configured set of potential DCCH resources, the UElistens on those resources in step 806. Next, in step 808, the UEdetermines if those resources are currently occupied by transmissions ofother UEs. For example, using energy detection on the DCCH resources,the UE can infer the presence of other transmitting UEs. In anotherexample, the UE can directly decode part or complete DCCH transmissionsfrom other transmitting UEs. In another alternative, the UE listens to asubset of DCCH resources and infers the occupancy level for the entireset of resources based on the measurement or reception on the subset.This can decrease complexity and increase efficiency of the channelaccess operation.

In the case where no other transmissions are detected, or if the powerof the detected transmissions are below a given threshold T_DCCH, a UEthen selects a subset of the DCCH resources to transmit its controlchannel message in step 812. In one embodiment, the subset definitioncan be predefined/configured or indicated via higher layer signaling(DSIB).

In option 2-1, the subset can correspond to the entire set of the DCCHresources.

Option 2-2 corresponds the subset to a fixed set of DCCH resources. Forexample, the subset of DCCH resources can correspond to M TDRSs or MTDRBs with MP=N, where P is the number of subsets and N is the number ofTDRS or TDRBs corresponding to a DCCH resource set. The subsets can befurther indexed according to frequency (e.g. lowest to highest infrequency) or time (earliest or latest timeslot)

In option 2-2A, the subset selection can start from the lowest index andcontinuously selects the next consecutive index; in option 2-2B, thesubset selection can start from the highest index and continuouslyselect the previous consecutive index; in option 2-2C, the subsetselection can start from a randomly selected index and continuouslyselect the next or previous consecutive index; and in option 2-2D, thesubset selection can start from an index j_dcch where j_dcch can beconfigured based on a higher layer configuration or based on a uniquevalue (e.g. D2D ID), and continuously select the next or previousconsecutive index.

Once the resource subset is selected according to one of the abovealternatives, the UE transmits the configured D2DCI in step 816.

Alternatively, in the case where the UE listens on potentially availableDCCH resources and detects the presence of other UEs, for example, ifthe power of the detected transmissions is above a given thresholdT_DCCH, the following alternatives are envisioned.

If all resources are determined to be occupied in step 810, the UEdetermines that channel access cannot succeed and configures a backofftimer in step 814. The backoff timer can indicate a number of time unitsor slots wherein the UE will not attempt to contend for the controlchannel in order to attempt to avoid further collisions. The value ofthe backoff timer can be preconfigured or indicated via higher layersignaling.

If for some resources Tx was not detected or if the power of thedetected transmissions on those resources are below a given thresholdT_DCCH, the UE can indicate those resources as unoccupied and select asubset of the unoccupied resources for DCCH transmission in step 812.One of option 2-1 and options 2-2A through 2-2D can be applied to theset of unoccupied resources. For example, indexing based selection ruleswill skip the subsets that are not in indicated as unoccupied.

In step 816, one UE transmits a D2DCI on a selected set of DCCHresources to another UE.

Time/Frequency Hopping

As mentioned previously, the allocation of control or data resources cancorrespond to a subset of time/frequency resource blocks. In one methodof operation, the frequency and time-slot pattern remains constantacross the broadcast transmission. However, to provide frequencydiversity and interference avoidance, time/frequency hopping can beutilized.

FIG. 10 illustrates an example time/frequency hopping pattern for twoUEs broadcast transmission resources, where a frequency shift and a timeshift are applied. The embodiment of the time/frequency hopping patternin FIG. 10 is for illustration only. Other embodiments could be usedwithout departing from the scope of the present disclosure.

In option 3-1, the time/frequency hopping pattern can be expressed as aseries of shifts relative to a starting frequency resource k (e.g. DTRB)and a starting time slot t (e.g. DTRS). In one example the frequencyshift can be expressed as k+s_(F) N_(F), where s_(F) is the appliedmultiple of N_(F) frequency resource blocks. Similarly the time shiftcan be expressed as a multiple s_(t) of N_(t) transmission instances.Alternately, more generally, the frequency shift and time shift can beexpressed as a single value (e.g. only the product of s_(F) N_(F) ors_(t) N_(t)).

In order to correctly decode all messages for which the above resourceallocation methods are applied, a common understanding betweentransmitting and receiving UEs of the applied time/frequency hoppingpattern is needed. In one embodiment, the time frequency hopping patterncan be indicated to the UE by explicitly providing the resources of allof the transmission resource blocks. In one alternative, the resourceblocks are indicated as a field in the D2DCI. In another alternative,subsets of resources can be indicated to correspond to one or moretransmission instances.

In option 3-1-1, the time/frequency hopping parameters can be indicatedinstead of the complete time/frequency resource allocation pattern. Thisis beneficial in reducing the overall amount of control overheadrequired. The set of indicated parameters which can be configuredinclude the reference starting frequency and/or transmission instance,frequency shift (e.g. s_(F) and N_(F)), and time shift (e.g. s_(t) andN_(t)). TABLE 1 gives an example of various fields conveying therelevant parameters. A set of time/frequency hopping parameters setforth in TABLE 1 indicates the time/frequency hopping pattern.

Various combinations of parameters can be envisioned depending on thetotal complexity of the time/frequency hopping and some parameters canbe implicitly determined or preconfigured. Additionally the parametersconsidered by configured independently or jointly.

TABLE 1 Field Description Reference starting DTRB k = {0, . . . N_(DTRB)− 1} Location of reference frequency DTRB (out of N_(DTRB) available)Reference starting DTRS (optional) t = {0, . . . N_(DTRS) − 1} Locationof reference frequency DTRS (out of N_(DTRS) available) Frequency shiftgranularity N_(F) = {1, . . . N_(DTRB)} Number of resources allocatedfor a given hopping instance Frequency shift multiple s_(F) ={−N_(F)/N_(DTRB), . . . N_(F)/N_(DTRB)} Factor of N_(F) DTRBs relativeto reference DTRB k Frequency shift periodicity {1, . . . 4} Number oftransmission instances for which the frequency hopping pattern isapplied Time shift granularity N_(t) = {1, . . . N_(DTRB)} Number ofresources allocated for a given hopping instance Time shift multiples_(t) = {−N_(t)/N_(DTRS), . . . , N_(t)/N_(DTRS)} Factor of N_(t) DTRBsrelative to reference DTRB t Time shift periodicity {1, . . . 4} Numberof transmission instances for which the time hopping pattern is applied

In addition, multiple methods of configuring the relevant time/frequencyhopping parameters are described below.

In option 3-1-2, the parameters, such as the ones described in TABLE 1can be preconfigured at the UE or statically configured by the network.In another alternative, the parameters can be conveyed via semi-statichigher layer signaling (e.g. RRC).

In option 3-1-3, the parameters can be configured by the UEautonomously. For example sets of time/frequency parameters cancorrespond to a range of D2D ID values. TABLE 2 gives an example D2D-IDbased hopping pattern mapping.

TABLE 2 D2D ID values N_(t), s_(t) N_(F), s_(F)  0-255 {1, 2} {5, 2} 256-511 {1, 2} {5, −2} 512-767 {1, 3} {5, −2}  768-1023 {1, 3} {5, −2}

In option 3-1-4, the parameters can be implicitly selected/configuredbased on the subset of transmission resources selected based on theabove Control Channel Design Access. For example, subsets of resourcescan be mapped to sets of time/frequency hopping parameters. TABLE 3gives an example mapping wherein DTRB/DTRS sets are mapped to hoppingparameters.

TABLE 3 DTRB/DTRS N_(t), s_(t) N_(F), s_(F) 0, 0 {1, 2} {5, 2}  0, 1 {1,2} {5, −2} 1, 0 {1, 3} {5, 2}  1, 1 {1, 3} {5, −2}

In option 3-1-5, a combination of parameter indication/configurationscan be utilized. For example, multiple parameters can be configured viahigher layer signaling, while another set is implicitly determined bymapping tables which are preconfigured or provided by higher layersignaling.

In option 3-2, the alternative hopping mapping pattern resourceallocation can be based upon an index set and a predefined symmetricfrequency hopping across transmission slots. Each allocation isassociated with an index m, where m can take a value {0, . . . N_DRB-1}.If a UE is allocated index m in time slot t, in time slot t+1 the userwill be allocated with the frequency symmetric DRB of the time tallocation, where the symmetric axis is given by [N_(DRB)/2] (i.e. DRBs{0, 1 . . . N_DRB/2-2, N_DRB/2-1} and {N_DRB-1, N_DRB-2 . . . N_DRB/2+1,N_DRB/2} represent symmetric sets if N_DRB is even and {0, 1 . . .N_DRB/2-2, N_DRB/2-1}{N_DRB-1, N_DRB-2 . . . N_DRB/2+1} if N_DRB is oddand {└N_(DRB)/2┘} is a self-symmetric set (i.e. no frequency hoppingbetween time slots). TABLE 4 gives an example hopping pattern for twotime slots and N_DRB=4 in the D2D broadcast communication.

TABLE 4 m = 3 m = 0 m = 2 m = 1 m = 1 m = 2 m = 0 m = 3 t = 0 t = 1

In option 3-3, the mapping can be from index m in slot t to index m_hopin slot t+1. In one example if m is even m_hop=m+1 and if m is oddm_hop=m−1. In another example m_hop=N_DRB−1−m. For example if N_DRB=4,this gives the same hopping pattern as in FIG. 8.

In option 3-4, the number of RBs per DRB can be mapped according to:

$\begin{matrix}{N_{RB}^{DRB} = \left\lfloor \frac{\left( {N_{RB}^{Total} - {\overset{\sim}{N}}_{RB}^{UL}} \right)}{N_{DRB}} \right\rfloor} & \left( {{Eq}.\mspace{14mu} 1} \right)\end{matrix}$where N_(RB) ^(Total) represents the total number of RBs in the systembandwidth and Ñ_(RB) ^(UL) represents the total number of RBs not usedby D2D operation. For example if PUCCH only is multiplexed with D2D thenN_(RB) ^(UL)=Ñ_(RB) ^(PUCHH) if Ñ_(RB) ^(PUCCH) is even, and Ñ_(RB)^(PUCCH)+1 if ÑRB^(PUCCH) is odd. If D2D and other cellular operationsare not time-multiplexed then Ñ_(RB) ^(UL)=0 or is not included in thisor any subsequent related equations.

In order to determine the RBs allocated for a given D2D UE based on theabove partitioning, a first index i_(PRB) ^(D2D) is indicated to the UEaccording to any of the prior indicated methods for resource allocation.For example, the options 2-2A through 2-2C can apply where i_(PRB)^(D2D) represents the UE-selected index (or is mapped to i_(PRB) ^(D2D)by a preconfigured mapping. In the case of the option 2-2D, i_(PRB)^(D2D) can be directly correspond to j_dcch explicitly or can beimplicitly derived from j_dcch if j_dcch is mapped to a a single or setof preconfigured values of i_(PRB) ^(D2D).

For a given slot t the allocation is given by:

$\begin{matrix}{{{n_{PRB}^{D\; 2D}(t)} = {{\left( {i_{PRB}^{D\; 2D} - \left\lceil \frac{{\overset{\sim}{N}}_{RB}^{UL}}{2} \right\rceil + {{f_{hop}(t)}N_{RB}^{DRB}}} \right){{mod}\left( {N_{RB}^{DRB}N_{DRB}} \right)}} + \left\lceil \frac{{\overset{\sim}{N}}_{RB}^{UL}}{2} \right\rceil}}\mspace{79mu}{where}} & \left( {{Eq}.\mspace{14mu} 2} \right) \\{{f_{hop}(t)} = \left\{ \begin{matrix}{0,} & {N_{DRB} = 1} \\{{\left( {{f_{hop}\left( {t - 1} \right)} + {\Delta\;{f_{hop}(t)}}} \right){mod}\; N_{DRB}},} & {N_{DRB} = 2} \\{{\left( {{f_{hop}\left( {t - 1} \right)} + {\Delta\;{f_{hop}(t)}{mod}\;\left( {N_{DRB} - 1} \right)} + 1} \right){mod}\; N_{DRB}},} & {N_{DRB} > 2}\end{matrix} \right\}} & \left( {{Eq}.\mspace{14mu} 3} \right)\end{matrix}$where Δƒ_(hop) is a hopping offset given by asΔƒ_(hop)(t)=(Σ_(k=10t+1) ^(10t+9) c(k)2^(k−(10t+1)))mod(N_(DRB)−1),Δƒ_(hop)(−1)=0  (Eq. 4)where the PN-sequence c(k) provides randomization and independenthopping for users by being initialized as c_int=D2DID.

In option 3-4, in addition to frequency hopping, mirroring can beapplied to further increase randomization of resource allocation betweenUEs. The value of the mirroring function ƒ_(m)t is based upon c(k):

$\begin{matrix}{{f_{m}(t)} = \begin{Bmatrix}{t\;{mod}\; 2} & {N_{DRB} = 1} \\{c\left( {10\; t} \right)} & {N_{DRB} > 1}\end{Bmatrix}} & \left( {{Eq}.\mspace{14mu} 5} \right)\end{matrix}$In the case of mirroring, the resource allocation for time slot t isgiven by:

$\begin{matrix}{{n_{PRB}^{D\; 2D}(t)} = {{\left( {i_{PRB}^{D\; 2D} - \left\lceil \frac{{\overset{\sim}{N}}_{RB}^{UL}}{2} \right\rceil + {{f_{hop}(t)}N_{RB}^{DRB}} + {\Delta\;{f_{m}(t)}}} \right){{mod}\left( {N_{RB}^{DRB}N_{DRB}} \right)}} + \left\lceil \frac{{\overset{\sim}{N}}_{RB}^{UL}}{2} \right\rceil}} & \left( {{Eq}.\mspace{14mu} 6} \right) \\{\mspace{79mu}{where}} & \; \\{{\Delta\;{f_{m}(t)}} = {\left( {\left( {N_{RB}^{DRB} - 1} \right) - {2\left( {\left( {i_{PRB}^{D\; 2D} - \left\lceil \frac{{\overset{\sim}{N}}_{RB}^{UL}}{2} \right\rceil} \right){mod}\; N_{RB}^{DRB}} \right)}} \right){{f_{m}(t)}.}}} & \left( {{Eq}.\mspace{11mu} 7} \right)\end{matrix}$

TABLE 5 gives an example of time/frequency hopping and mirroring patternaccording to the above option 3-3 and option 3-4 for N_(RB) ^(Total)=12,N_(RB) ^(DRB)=3, N_(DRB)=4. For simplicity, only three RBs within theDiscovery Resource Blocks (DRBs) are marked with bracketed numbers toindicate the hopping between the two slots.

TABLE 5 DRB = 0, RB = 0 [1] DRB = 0, RB = 0 DRB = 0, RB = 1 DRB = 0, RB= 1 [2] DRB = 0, RB = 2 DRB = 0, RB = 2 DRB = 1, RB = 3 DRB = 1, RB = 3[3] DRB = 1, RB = 4 DRB = 1, RB = 4 DRB = 1, RB = 5 DRB = 1, RB = 5 DRB= 2, RB = 6 DRB = 2, RB = 6 [1] DRB = 2, RB = 7 [2] DRB = 2, RB = 7 DRB= 2, RB = 8 DRB = 2, RB = 8 DRB = 3, RB = 9 DRB = 3, RB = 9 DRB = 3, RB= 10 DRB = 3, RB = 10 DRB = 3, RB = 11 [3] DRB = 3, RB = 11 t = 0 t = 1,f_(hop) = 1, f_(m) = 1

Resource Allocation Indication

The time and/or frequency hopping parameters can be indicated to thereceiving UEs by one of the following options.

In option 4-1, parameters can be indicated in fields contained in theD2DCI.

In option 4-2, the hopping pattern can be indicated in a higher layercontrol message (e.g. MAC scheduling).

In option 4-3, the parameters can be implicitly indicated. For example,if the control message is received on a given subset of DTRB/DTRS, thereceiving UE can determine a mapping between those resources and thesubsequent time/frequency hopping pattern.

In option 4-4, the parameters can be a function of the D2DIdentification (ID).

In option 4-5, the parameters can be statically preconfigured by thenetwork or hardcoded.

The applicability of frequency/time hopping methods described can be forboth and control and data channels. In one alternative, the parametersand configurations can be jointly applied. However since control anddata reception can be decoupled and require different levels ofrobustness, different hopping configurations can be applied to controland data channels.

In option 4-6, one or more higher layer configuration parameters areindicated by higher layer signaling (e.g. RRC) hoppingD2D can indicateto the UE whether a given time/frequency configuration is applied.

In option 4-6A, one or more higher layer configuration parameters forcontrol and data channels are indicated separately by higher layersignaling (e.g. RRC). In this case dcchHoppingD2D can indicate to the UEwhether a given time/frequency configuration is applied for the controlchannel while dbchHoppingD2D can indicate to the UE whether a giventime/frequency configuration is applied for the data channel.

In option 4-6B, one or more higher layer configuration parameters areused for control channel hopping pattern indication and the hoppingpattern indication for the data channel is indicated separately by L1signaling (e.g. MAC or D2DCI). This potentially provides a transmittingUE with more flexibility to adapt to changing interference orenvironments.

In option 4-6C, one or more higher layer configuration parameters areused for frequency hopping pattern indication and separate parametersare used for time hopping pattern indication. Any of the previousalternatives concerning separate or joint indication for control anddata channels can also be combined in this case. For example fourparameters could be configured for a UE: dcchFreqHoppingD2D,dcchTimeHoppingD2D, dbchFreqHoppingD2D, dbchTimeHoppingD2D.

It should be noted that any of the above indications can directlyindicate whether a pattern is applied and also indicate directly or withdependent subfields the exact values of relevant time/frequency hoppingparameters. Alternatively the configuration parameters can indicatewhether a particular time/frequency hopping pattern is applied as wellas an index which maps to a set of parameter values. In a furtheralternative, the configuration parameters can only indicate whethertime/frequency hopping is applied and values of the parameters areindicated by another method or are preconfigured at the UE.

The following embodiment describes a complete broadcast operationprocedure combining the previously described methods. In thisembodiment, a single UE1 will transmit a broadcast message which isreceived by UE2 while both devices are outside of network coverage. Itcan be understood that in this example does not preclude constructingfurther exemplary embodiments from different combinations of the abovemethods.

Step 1 is synchronization and initialization: in this step, UEs areinitially configured with D2DIDs and group associations as well asobtaining an indication of reserved frequency bandwidth and subframesfor D2D operation. Synchronization is assumed to be obtained between thetwo UEs either by an internal or external timing reference (e.g. syncsignals from UE1 to UE2).

Step 2 is control channel access: UE1 determines to transmit a broadcastmessage and first determines resources for transmitting on the controlchannel. UE1 listens on the preconfigured set of control channelresources and based on the absence or presence of a control channelbeacon transmitted by other UEs selects a subset of resources fortransmitting a control channel. Based on the selected subset afrequency/time hopping pattern is configured for determining the exactresource allocation necessary to transmit the control information.

Step 3 is control channel reception: UE2 is preconfigured with a set ofpotential resources where a UE can transmit control information. Basedon this preconfiguration, UE2 searches over the entire set for anycontrol channel transmissions and detects the transmission of UE1 andcan decode the entire transmission based on the common understanding ofthe frequency/time hopping pattern implicitly indicated by UE2.

Step 4 is data channel transmission: UE1 subsequently transmits onselected data channel resources and initializes and applies the datachannel frequency/time hopping pattern based on its D2DID (which wasbroadcast to UE2 in the D2DCI in the step 1.

Step 5 is data channel reception: UE2 is able to decode the data channeltransmissions of UE1 by following the time/frequency hopping patternimplicitly indicated by UE1 by broadcasting the D2DID in the controlchannel information received in the step 2.

It can be also contemplated that various combinations orsub-combinations of the specific features and aspects of the embodimentsmay be made and still fall within the scope of the appended claims. Forexample, in some embodiments, the features, configurations, or otherdetails disclosed or incorporated by reference herein with respect tosome of the embodiments are combinable with other features,configurations, or details disclosed herein with respect to otherembodiments to form new embodiments not explicitly disclosed herein. Allof such embodiments having combinations of features and configurationsare contemplated as being part of the present disclosure. Additionally,unless otherwise stated, no features or details of any of theembodiments disclosed herein are meant to be required or essential toany of the embodiments disclosed herein, unless explicitly describedherein as being required or essential.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method, comprising: scheduling at least oneresource for a Device-to-Device (D2D) transmission control channel(DCCH) carrying a D2D control information (D2DCI) message; transmitting,by a first UE, the DCCH on the at least one DCCH resource to at leastone second UE; scheduling at least one resource for a D2D data channel(DDCH); transmitting, by the first UE, the DDCH on the at least one DDCHresource to the at least one second UE, wherein the DCCH is transmittedaccording to a time and frequency hopping pattern based on a hoppingparameter; listening, by the first UE, on a configured set of potentialresources for the DCCH to detect a transmission by another UE; in a casewhere the transmission by another UE is not detected, or a power of thetransmission by another UE is below a given threshold, selecting, by thefirst UE, a subset of the set of potential DCCH resources as the atleast one DCCH resource; and in a case where the transmission by anotherUE is detected, or the power of the transmission by another UE is abovethe given threshold, configuring a backoff timer indicating a number oftime units or slots during which the first UE will not attempt tocontend for the at least one DCCH resource.
 2. The method of claim 1,wherein the DDCH comprises a D2D broadcast channel (DBCH).
 3. The methodof claim 1, wherein the subset of the set of potential DCCH resources ispredefined or configured or indicated via higher layer signaling.
 4. Themethod of claim 1, wherein subsets of the set of potential DCCHresources are indexed in an order of frequency, and the subset selectionstarts from one of: the lowest index, the highest index, a randomlyselected index, and an index that is configured based on a higher layerconfiguration or a D2D identification (ID).
 5. The method of claim 1,wherein at least one of the DCCH and the DDCH is configured according toa time and frequency hopping pattern defined by time and frequencyhopping parameters.
 6. The method of claim 5, wherein sets of the timeand frequency hopping parameters correspond to ranges of D2D ID values.7. The method of claim 5, wherein either of a higher layer and a L1layer signals one or multiple higher layer configuration parametersindicating whether each of the DCCH and DDCH have a time and frequencyhopping pattern separately.
 8. The method of claim 7, wherein themultiple configuration parameters comprise a first higher layerconfiguration parameter indicating whether a time and frequency hoppingconfiguration applies to the DCCH, and a second higher layerconfiguration parameter indicating whether a time and frequency hoppingconfiguration applies to the DDCH.
 9. The method of claim 7, wherein themultiple higher layer configuration parameters comprise a frequencyhopping pattern indicator and a time hopping pattern indicator for DCCH,and a time hopping pattern indicator and a frequency hopping patternindicator for DDCH.
 10. A user equipment (UE) configured for D2Dcommunications, the UE comprising: one or multiple antenna; and aprocessing circuitry configured to: schedule at least one resource for aDevice-to-Device (D2D) transmission control channel (DCCH) carrying aD2D control information (D2DCI) message; transmit the DCCH on the atleast one DCCH resource, to at least one second UE through the one ormore multiple antenna; schedule at least one resource for a D2D datachannel (DDCH); and transmit the DDCH on the at least one DDCH resource,to the at least one second UE, wherein the DCCH is transmitted accordingto a time and frequency hopping pattern based on a hopping parameter;listen through the one or multiple antenna on a configured set ofpotential resources for the DCCH to detect a transmission by another UE;in a case where the transmission by another UE is not detected, or apower of the transmission by another UE is below a given threshold,select a subset of the set of potential DCCH resources as the at leastone DCCH resource; and in a case where the transmission is detected, orthe power of the transmission is above the given threshold, configure abackoff timer indicating a number of time units or slots during whichthe UE will not attempt to contend for the DCCH.
 11. The UE of claim 10,wherein the DDCH comprises a D2D broadcast channel (DBCH).
 12. The UE ofclaim 10, wherein the subset of the set of potential DCCH resources ispredefined or configured or indicated via higher layer signaling. 13.The UE of claim 10, wherein subsets of the set of potential DCCHresources are indexed in an order of frequency, and the subset selectionstarts from one of: the lowest index, the highest index, a randomlyselected index, and an index that is configured based on a higher layerconfiguration or a D2D identification (ID).
 14. The UE of claim 10,wherein at least one of the DCCH and the DDCH is configured according toa time and frequency hopping pattern defined by time and frequencyhopping parameters.
 15. The UE of claim 14, wherein sets of the time andfrequency hopping parameters correspond to ranges of D2D ID values. 16.The UE of claim 14, wherein either of a higher layer and a L1 layersignals one or multiple higher layer configuration parameters indicatingwhether each of the DCCH and DDCH have a time and frequency hoppingpattern separately.
 17. The UE of claim 16, wherein the multipleconfiguration parameters comprise a first higher layer configurationparameter indicating whether a time and frequency hopping configurationapplies to the DCCH, and a second higher layer configuration parameterindicating whether a time and frequency hopping configuration applies tothe DDCH.
 18. The UE of claim 16, wherein the multiple higher layerconfiguration parameters comprise a frequency hopping pattern indicatorand a time hopping pattern indicator for DCCH, and a time hoppingpattern indicator and a frequency hopping pattern indicator for DDCH.19. A user equipment (UE) configured for D2D communications, the UEcomprising: one or more multiple antenna; and a processing circuitryconfigured to: receive at least one resource for a Device-to-Device(D2D) transmission control channel (DCCH) carrying a D2D controlinformation (D2DCI) message through the one or more multiple antennafrom a first UE; receive at least one resource for a D2D data channel(DDCH) based on DCCH through the one or more multiple antenna from thefirst UE, wherein the at least one resource is received by the UE fromthe first UE based on the first UE: listening, by the first UE, on aconfigured set of potential resources for the DCCH to detect atransmission by the UE; in a case where the transmission by the UE isnot detected, or a power of the transmission by the UE is below a giventhreshold, selecting, by the first UE, a subset of the set of potentialDCCH resources as the at least one DCCH resource; and in a case wherethe transmission by the UE is detected, or the power of the transmissionby the UE is above the given threshold, configuring a backoff timerindicating a number of time units or slots during which the first UEwill not attempt to contend for the at least one DCCH resource; anddemodulate and decode at least one DDCH resource, using the D2DCImessage, wherein the DCCH is received according to a time and frequencyhopping pattern based on a hopping parameter.
 20. The UE of claim 19,wherein at least one of the DCCH and the DDCH is configured according toa time and frequency hopping pattern defined by time and frequencyhopping parameters.
 21. The UE of claim 19, wherein sets of the time andfrequency parameters correspond to ranges of D2D ID values.
 22. The UEof claim 19, wherein either of a higher layer and a L1 layer signals oneor multiple higher layer configuration parameters indicating whethereach of the DCCH and DDCH have a time and frequency hopping patternseparately.
 23. The UE of claim 22, wherein the multiple configurationparameters comprise a first higher layer configuration parameterindicating whether a time and frequency hopping configuration applies tothe DCCH, and a second higher layer configuration parameter indicatingwhether a time and frequency hopping configuration applies to the DDCH.24. The UE of claim 22, wherein the multiple higher layer configurationparameters comprise a frequency hopping pattern indicator and a timehopping pattern indicator for DCCH, and a time hopping pattern indicatorand a frequency hopping pattern indicator for DDCH.